It has become common practice to provide the electrical wiring in buildings by means of modular wiring systems composed of electrical cables having cable connectors on their ends, T-shaped junction connectors, and tap connectors. The cable connectors are coupled to the junction connectors at locations where electrical outlets are required and a tap connector is coupled to the junction connector. Tap conductors in the junction connector extend from the feed-through conductors in the junction connector to the mating face of the tap connector so that the terminals in the tap connector are mated with terminals on the ends of the tap conductors in the junction connector. The terminals in the tap connector in turn are connected to wires which extend to the lighting or other equipment being supplied with electrical power. U.S. Pat. No. 4,146,287 shows a typical modular wiring system and shows details of the connectors used in the system.
Ordinarily, five separate conductors are provided in each cable of the wiring system so that five feed-through conductors must be provided in the junction connectors. Electrical taps to the feed-through conductors usually require only three or four conductors so that a typical electrical junction will have three or four tap conductors connected to, and extending from, the feed-through conductors in the junction connector. The tap conductors must be selectively connected to the junction conductors and different combinations of feed-through conductors must be connected to the tap conductors in different electrical taps in a wiring system.
In accordance with the teachings of U.S. Pat. No. 4,146,287, the tap conductors are formed integrally with the feed-through conductors so that for every tap connection a special type of feed-through and tap conductor is required. As a result, a relatively large number of different types of conductors for the junction connector are required to provide every requirement for a wiring system. It would be desirable to have feed-through conductors and tap conductors of standard types which can be assembled to each other in a manner such that any possible combination of connections between the feed-through and tap conductors could be achieved. The present invention, in accordance with one aspect thereof, is directed to the achievement of feed-through and tap conductors which are of standard shapes and sizes but which can be readily connected to each other to yield any desired electrical connections between the tap conductors and the feed-through conductors in the junction connector.
The tap connector which is coupled to the junction connector shown in U.S. Pat. No. 4,146,287 has a rectangular cross-section, as does the junction connector. It is convenient in modular wiring systems to arrange the feed-through conductors in the junction connector in side-by-side parallel coplanar relationship and it is also convenient to arrange the tap conductors in the same manner in the tap connector. However, it would be preferable to be able to use cylindrical tap connectors of a size dimensioned to be fitted into standard size openings which are provided in lighting fixtures and other electrical equipment by the equipment manufacturer. When the conductors in the tap connector are arranged in a single row and the tap connector has a rectangular cross-section, it is therefore necessary to use a special adaptor in the lighting fixture or to otherwise mount the tap connector in the fixture. In accordance with the present invention, the ends of the tap conductors are arranged as a non-linear cluster and the terminal ends of these tap conductors can be mated with terminals in a cylindrical tap connector.
A preferred form of feed-through conductor for junction connectors in accordance with the invention, comprises a flat rectangular stamped member of conductive metal having ends which serve as terminals that are mated with complementary terminals in the cable connectors of the system. Three aligned holes are provided in the feed-through conductor and a slot is formed therein which intersects the three holes. The material of the conductor on each side of the slot is coined outwardly from one surface of the conductor so that this material has a generally cylindrical surface adjacent to the holes and on each side of the slot. The tap conductors comprise rods which are dimensioned to be inserted through one of the holes in a feed-through conductor and have a tight interference fit. The presence of the slot in the feed-through conductor and the outward coining of the metal on each side of the slot results in the development of torsional stresses in these coined portions when the end of the tap conductor is inserted through a hole in the feed-through conductor. The torsional stresses produce contact forces at the electrical interface which are substantially in excess of the forces which would be achieved with a simple punched hole for the tap conductor.
The tap conductors are either straight or have an intermediate portion which extends normally of the two ends so that the remote end from the feed-through conductor is offset from the end of the tap conductor which is connected to the feed-through conductor. The use of tap conductors having these offset free ends and the provision of the three holes in each feed-through conductor permits the arrangement of the free ends of the feed-through conductors as a cluster, rather than an aligned array.